1. Technical Field
The present invention relates to apparatus and method for supporting and positioning inert electrodes in electrolytic reduction cells for the production of aluminum.
2. Description of Conventional Art
The electrolytic reduction smelting of aluminum involves an electrochemical oxidation and reduction reaction associated with the decomposition of alumina dissolved in cryolite electrolyte bath. The electrolyte bath in such a process is a fluoride-ion-containing molten metal solution which is very corrosive.
The production cells for the electrolytic smelting of aluminum according to the Hall-Heroult process have been the subject of novel electrode designs recently. For example, U.S. patent application Ser. No. 488,783, filed April 26, 1983, U.S. Pat. No. 4,664,760 by Noel Jarrett involves a novel electrolytic cell and method of electrolysis using supported electrodes. The Jarrett patent application addresses a significant problem which develops in standard commercial practice for producing aluminum, which is exemplified in fluoride-containing electrolyte bath electrolysis as in the Hall-Heroult process, when the electrode is supported by the floor or wall of the electrolytic cell. This problem derives from a warping of the internal surfaces of the cell, e.g., the floor or the wall, which occurs during the operation of the aluminum-producing cell under the normally harsh operating conditions of electrolytic smelting of alumina dissolved in cryolite electrolyte bath. Such warping will destroy a specified and particular electrode placement or positioning when the electrodes are fixed to or supported by the wall or floor of the cell. The Jarrett patent application provides a remedy for these problems by achieving and operating an electrolytic cell having a specified anode-cathode distance which can be maintained very small over a longer period of time than previously possible. In fact, the Jarrett invention provides an ability to establish an inter-electrode zone having a specified dimension which is essentially fixed.
However, there is a need for providing a spacer between the anode and cathode in a monopolar electrode assembly or between adjacent bipolar electrode surfaces in a bipolar electrode assembly in an electrolytic cell adapted to employ a specified anode-cathode distance.
It is an object of the present invention to provide a corrosion-resistant positioning means for electrodes immersed in a corrosive chemical bath, e.g., such as a fluoride-containing electrolyte bath in an aluminum smelting electrolysis cell.
It is a further object of the present invention to provide a spacer for positioning adjacent anode surfaces and cathode assemblies in monopolar and bipolar electrode assemblies to provide a specified anode-cathode distance and which will not be destroyed by the combinations of molten aluminum and fluoride-containing molten metal bath at the cathode and oxygen and fluoride-containing bath at the anode.
These and other objects of the present invention will become evident from the detailed description which follows.